1. Field of the Invention
This invention relates to methods of analyzing and optimizing design of integrated circuit (IC) designs.
2. Description of the Related Art
An integrated circuit chip (hereafter referred to as an xe2x80x9cICxe2x80x9d or a xe2x80x9cchipxe2x80x9d) comprises cells and connections between the cells formed on a surface of a semiconductor substrate. The IC may include a large number of cells and require complex connections between the cells.
A cell is a group of one or more circuit elements such as transistors, capacitors, and other basic circuit elements grouped to perform a function. Each of the cells of an IC may have one or more pins, each of which, in turn, may be connected to one or more other pins of the IC by wires. The wires connecting the pins of the IC are also formed on the surface of the chip.
A net is a set of two or more pins which must be connected, thus connecting the logic circuits having the pins. Because a typical chip has thousands, tens of thousands, or hundreds of thousands of pins, that must be connected in various combinations, the chip also includes definitions of thousands, tens of thousands, or hundreds of thousands of nets, or sets of pins. The number of the nets for a chip is typically in the same order as the order of the number of cells on that chip. Commonly, a majority of the nets include only two pins to be connected; however, many nets comprise three or more pins.
The present invention is a method and apparatus for optimizing the design of a combinational circuit. The method includes constructing a circuit sheaf for the combinational circuit and then performing vector optimization with domination. In the preferred embodiment, a complete BDD B is determined and, from that, a list of F-sets is computed. If the combinational circuit includes cells other than NOT, AND and XOR cells, the circuit is first transformed such that it only has those types of cells.